Effect of Structure Flexibility on Attitude Dynamics of Modernizated Microsatellite

1
Effect of Structure Flexibility on Attitude
Dynamics of Modernizated Microsatellite
2
Overview

• Research Objectives and Tasks
• Micro satellite Configuration
• Reference frames
• Mathematical Models of flexible space structures
• Major Findings and Results
• Recommendations for Future Research

3
Research Objectives and Tasks

• The major objective of this research is to study
  the effect of structure flexibility on attitude
  behavior (Euler angles and angular velocities )
  of micro satellites and the degree of such effect

4
Research Objectives and Tasks

• The research objectives and tasks of this study
  are as follows
• Develop mathematical models of flexible space
  structures
• Determine the attitude accuracy

5
Micro Satellite Configuration

• The construction of micro satellite can consist
  of main parts base plate, mounting plate, walls,
  blocks and the payloads.
• Each part and subpart of this construction will
  be replaced by the equivalent solid mass and
  moment of inertia with respect to the real
  construction.

6
Micro Satellite Configuration
7
Micro Satellite Configuration
8
Reference Frames

• Inertial coordinate system (ICS)
• Orbital coordinate system (OCS)
• Design coordinate system (DCS)
• Body axes system (BAS)

9
Mathematical Models of Flexible Space Structures

• A mathematical model of the satellite takes into
  account flexible body components (solar panels,
  antennas, booms etc)
• This kind of modelling consists of two parts one
  related to rigid body motion and the other to
  flexible body motion.

10
Mathematical Models Of Flexible Space Structures

• Two kind of software will be used ANSYS and
  MATLAB
• ANSYS software will be used to calculate the
  modal analysis (natural frequencies and mode
  shapes)
• MATLAB software will be used to integrate the
  system of equations .

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Mathematical Models Of Flexible Space Structures
Finite Element Model
12
Mathematical Models Of Flexible Space Structures

• The dynamic equations of motion around center of
  mass taken into account the elastic oscillations
  of a housing of satellite and solar panels can be
  written in the following form

13
Mathematical Models Of Flexible Space Structures
The calculation of flexible modes elements (Gai)
are usually determined by the following way in
BAS ?b is a radius vector that connects
satellite COM to any arbitrary point of the
satellite construction Uai is a vector to
describe the mode shape.
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Mathematical Models Of Flexible Space Structures
Lines of micro satellite used for representing
flexible elements.
15
Mathematical Models Of Flexible Space Structures

• The satellite kinematics equations will be in the
  following form

?bo is the satellite body angular velocity with
respect to the OCS ?, ?,? are EULER angles
pitch, roll and yaw respectively.
16
Finding and Major Results

• Average values for frequencies (fi) for the first
  six tones groups are equal to 14 26.7 65.5
  86.9 90.2 113 Hz respectively
• It is noted that the first five tones groups is
  related to the solar panels of the satellite and
  at the group tone number six is for the housing.

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Finding and Major Results
26.99 HZ
26.85 HZ
27.02 HZ
27.03 Hz
Micro satellite solar panels 2nd tones groups.
18
Finding and Major Results
113.36 HZ
Micro satellite housing 1st tone.
19
Finding and Major Results

• The simulations of satellite dynamics (Euler
  angles and angular velocities) is carried out
  using MATLAB software on the following two cases
  
• On the satellite as a RIGID BODY
• On the satellite as a FLEXIBLE BODY (taking into
  account vibration modes of the satellite)

20
Finding and Major Results

• On both the above situations the gravitational
  moment is the only external moment
• Result of simulation are shown in the following
  figures. From this results it is noted that their
  is unobserved different between rigid and
  flexible body simulations

21
Finding and Major Results
Simulation of attitude dynamics (angular
velocities) with and without flexible moments
22
Finding and Major Results
Simulation of attitude dynamics (Euler angles )
with and without flexible moments
23
Finding and Major Results
Error of attitude dynamics (Euler angles and
angular velocities) due to flexible moment in 20
sec
24
Recommendations For Future Research

• Recommendations for designers and engineers
  concerning the satellite structure flexibility
  necessities within the framework of the following
  
• Resolution requirements of the payload
• Satellite attitude accuracy requirements
• Satellite structural layout diagram